For a complex signal such as an echo signal, the phase of the complex signal may be extracted using an inverse trigonometric function, which may make the phase be wrapped into a range of 2π and make an image generated based on the phase having artifacts. In order to improve the quality of the image, phase unwrapping may be performed. Phase unwrapping may refer to the process of determining the actual phase of a complex signal. However, there are some problems such as inaccuracy or lack of robustness in existing methods and apparatuses for phase unwrapping. Therefore, it is desirable to provide methods and apparatuses for accurate phase unwrapping.